Method and system for providing a smaller critical dimension magnetic element utilizing a single layer mask

ABSTRACT

The method and system for providing a magnetic element are disclosed. The method and system include providing a magnetic element stack that includes a plurality of layers and depositing a stop layer on the magnetic element stack. The method and system also include providing a dielectric antireflective coating (DARC) layer on the stop layer, forming a single layer mask for defining the magnetic element on a portion of the DARC layer, and removing a remaining portion of the DARC layer not covered by the single layer mask. The portion of the DARC layer covers a portion of the stop layer. The method further includes removing a remaining portion of the stop layer and defining the magnetic element using at least the portion of stop layer as a mask.

FIELD OF THE INVENTION

The present invention relates to magnetic recording technology, and moreparticularly to a method and system for providing a magnetic elementcapable of having a smaller critical dimension using a single layermask.

BACKGROUND

FIG. 1 depicts a conventional method 10 for providing a conventionalmagnetic element, such as magnetoresistive elements used in readtransducers. FIGS. 2-3 depict the conventional magnetic element duringfabrication. Referring to FIGS. 1-3, the layers for the conventionalmagnetic element are deposited, via step 12. For a conventionaltunneling magnetoresistance (TMR) stack that may be used in a readtransducer, step 12 may include depositing a pinning layer such as anantiferromagnetic (AFM) layer, a pinned layer, a nonmagnetic spacerlayer, and a free layer. The pinned and free layers are typicallyferromagnetic or synthetic antiferromagnetic layers including twoferromagnetic layers separated by a nonmagnetic, conductive layer. For aconventional TMR stack, the nonmagnetic spacer layer is an insulator,such as Al₂O₃, crystalline MgO, and/or titanium oxide, that provides atunneling barrier.

A conventional undercut bilayer structure is provided on theconventional magnetic element layers, via step 14. FIG. 2 depicts theconventional magnetic element layers 20 and the conventional undercutbilayer structure 30. The conventional magnetic element layers 20include an AFM layer 22, a pinned layer 24, an insulating, nonmagneticspacer layer 26, and a free layer 28. Other layers, such as seed orcapping layers, might also be used. The conventional undercut bilayerstructure 30 includes two layers 32 and 34. The lower layer is typicallya PMGI layer 32, while the upper layer is typically a photoresist layer34. The PMGI layer 32 is narrower than the photoresist layer 34 toprovide the undercut 36.

The pattern provided by the conventional undercut bilayer structure 30is transferred to the underlying magnetic element layers 20, via step16. In step 16, therefore, the magnetic element is defined. FIG. 3depicts the conventional magnetic element 20′ that has been formed priorto removal of the conventional undercut bilayer structure 30. Theconventional magnetic element 20′ has been defined from the layers 22′,24′, 26′, and 28′.

Processing is completed for the conventional magnetic element 20′ andthe conventional device in which the conventional magnetic element 20′resides, via step 18. Step 18 includes lifting off the conventionalundercut bilayer structure 30, which exposes the underlying conventionalmagnetic element 20′. Step 18 may also include providing subsequentlayers and processing steps. For example, insulating layers, hard biaslayers, fillers, and contacts to the conventional magnetic element 20′may be provided in step 18. Typically, these layers are provided priorto lift-off of the conventional undercut bi-layer structure 30 so thatthe conventional undercut bi-layer structure 30 can act as a mask forthe conventional magnetic element 20′. Thus, the conventional magneticelement 20′ in a conventional device, such as a read transducer and/ormerged head, may be formed.

Although the conventional method 10 and the conventional magneticelement 20′ can function, one of ordinary skill in the art will readilyrecognize that the trend in magnetic recording technology is towardhigher densities and smaller sizes. Thus, the critical dimensions inwrite or read heads are currently below those in semiconductorprocessing. Further, as sizes shrink to provide areal densities above120 Gb/in², the lift-off performed in step 18 becomes more difficult.For printed critical dimensions of the photoresist layer 34 below 0.1micrometer, it is difficult to provide a small enough the PMGI layer 32to generate a sufficient undercut for lift-off. For example, theundercut 36 must typically be greater than at least 0.03 micrometer forcomplete liftoff of the conventional undercut bilayer structure 30. Thismeans that the PMGI layer 32 is only 0.04 micrometers in width for a 0.1micrometer photoresist layer 34. For smaller geometries having criticaldimensions of less than 0.1 micrometer, the PMGI layer 32 may become toothin to support the photoresist layer 34, causing the conventionalundercut bilayer structure 30 to collapse. Thus, transfer of the patternof the conventional undercut bilayer structure 30 to the conventionalmagnetic element 20′ and liftoff of the conventional undercut bilayerstructure 30 become difficult. For areal densities of 200 Gb/in² andtrack widths of 0.08 micrometer or less, the conventional method 10 andconventional undercut bilayer structure 30 may be incapable offabricating the conventional magnetic element 20′.

Accordingly, what is needed is a system and method for providing amagnetic element having smaller critical dimensions.

SUMMARY

A method and system for providing a magnetic element are disclosed. Themethod and system comprise providing a magnetic element stack thatincludes a plurality of layers and depositing a stop layer on themagnetic element stack. The method and system also comprise providing adielectric antireflective coating (DARC) layer on the stop layer,forming a single layer mask for defining the magnetic element on aportion of the DARC layer, and removing a remaining portion of the DARClayer not covered by the single layer mask. The portion of the DARClayer covers a portion of the stop layer. The method further includesremoving a remaining portion of the stop layer and defining the magneticelement using at least the portion of stop layer as a mask.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a flow chart depicting a conventional method for providing aconventional magnetic element.

FIG. 2 depicts a conventional magnetic element during fabrication.

FIG. 3 depicts a conventional magnetic element during fabrication.

FIG. 4 is a flow chart depicting a method in accordance with anexemplary embodiment of the present invention for fabricating a magneticelement.

FIG. 5 is a diagram of a magnetic element during fabrication inaccordance with an exemplary embodiment of the present invention.

FIG. 6 is another diagram of the magnetic element during fabrication inaccordance with an exemplary embodiment of the present invention.

FIG. 7 is another diagram of the magnetic element during fabrication inaccordance with an exemplary embodiment of the present invention.

FIG. 8 is another diagram of the magnetic element during fabrication inaccordance with an exemplary embodiment of the present invention.

FIG. 9 is another diagram of the magnetic element during fabrication inaccordance with an exemplary embodiment of the present invention.

FIG. 10 is another diagram of the magnetic element during fabrication inaccordance with an exemplary embodiment of the present invention.

FIG. 11 is another diagram of the magnetic element during fabrication inaccordance with an exemplary embodiment of the present invention.

FIG. 12 is another diagram of the magnetic element during fabrication inaccordance with an exemplary embodiment of the present invention.

FIG. 13 is another diagram of the magnetic element during fabrication inaccordance with an exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 4 is a flow chart depicting a method 100 in accordance with anotherexemplary embodiment of the present invention for fabricating a magneticelement. FIGS. 5-13 depict a magnetic element residing in a transducer200 during fabrication in accordance with an exemplary embodiment of thepresent invention. The method 100 is described in the context of aparticular magnetic element, a TMR stack. However, one of ordinary skillin the art will readily recognize that the method 100 can be used inconjunction with other magnetic elements such as spin valves. Inaddition, steps may be omitted or combined for ease of explanation.Further, fabrication of the magnetic element is described in the contextof a transducer 200. However, in an alternate embodiment, the magneticelement may be used in a different device.

The layers for the magnetic element are deposited, via step 102. In apreferred embodiment, step 102 includes depositing a pinning layer suchas an AFM layer, a pinned layer, a spacer layer, and a free layer. Thepinned layer and free layer may be simple ferromagnetic layers or may bysynthetic antiferromagnets including ferromagnetic layers separated byconductive nonmagnetic layer(s). The spacer layer is preferably aninsulator and acts as a tunneling barrier. In addition, seed and/orcapping layers may be provided in step 102. Although the magneticelement layers provided in step 102 are preferably for a TMR stack, inanother embodiment, the layers could be for another magnetic element.

A stop layer is deposited on the magnetic element layers, via step 104.The stop layer is preferably used as a chemical mechanical polish (CMP)stop. In a preferred embodiment, the stop layer provided in step 104 isa diamond-like carbon (DLC) layer. However, in another embodiment, othermaterial(s) may be used. A dielectric antireflective coating (DARC)layer is provided on the stop layer, via step 106. As its name suggests,the DARC layer is an antireflective layer configured to reducereflections during photolithographic processes. In addition, the DARClayer preferably improves adhesion of a subsequent mask layer. Also in apreferred embodiment, the DARC layer is resistant to etches used toremove the subsequent mask layer.

A single layer mask is provided, via step 108. Step 108 includesdepositing and developing the single layer mask where photoresist isused for the single layer mask. In a preferred embodiment, step 108optionally also includes trimming the single layer mask to furtherreduce the critical dimension of the single layer mask.

FIG. 5 depicts the transducer 200 after at least a portion of step 108has been performed. The transducer 200 is depicted before trimming, ifany, in step 108 is performed. Shown in FIG. 5 are magnetic elementlayers 210, stop layer 220, DARC layer 230, and single layer mask 240.In the embodiment shown, the magnetic element layers 210 reside on ashield 202. In the embodiment shown, the magnetic element layers 210include an AFM layer 212, a pinned layer 214, an insulator spacer layer216, and a free layer 218. Note that although a particular orientationof the layers 212, 214, 216, and 218 with respect to the shield 202 isshown, another orientation could be used. For example, the orientationof the layers 212, 214, 216, and 218 could be reversed. The stop layer220 depicted is preferably a DLC layer. However, in an alternateembodiment, the stop layer 220 could include other materials such as Ta,W, alumina, and/or silicon dioxide. The DARC layer 230 preferablyincludes at least one or more of SiO₃, Si_(x)N₄ and SiO_(x)N_(y).However, in another embodiment, the DARC layer 230 may include othermaterials or combinations of materials such as SiO₃, Si_(x)N₄ andSiO_(x)N_(y). In a preferred embodiment, the DARC layer 230 improvesadhesion of the single layer mask 240. The single layer mask 240 ispreferably a deep ultraviolet (DUV) photoresist mask. The DARC layer 230is, therefore, preferably configured to reduce reflections of the DUVlight used in developing the single layer mask 240. In one embodiment,the single layer mask 240 is developed to have a critical dimension, d,of approximately 0.1 μm, at the lower limit of photolithography usingDUV photoresist. In another embodiment, the single layer mask 240 mayhave a different critical dimension.

FIG. 6 depicts the transducer 200 after step 108 has been completed.Thus, the transducer 200 is depicted after the trimming has beenperformed in a preferred embodiment of step 108. If DUV photoresist isused for the single layer mask 240, the trimming of the single layermask may be performed using an oxygen plasma reactive ion etch (RIE). Asa result, the single layer mask 240′ is still present, but has a smallercritical dimension. In one embodiment, the critical dimension of thesingle layer mask 240′ is approximate 0.08 μm. In a preferredembodiment, the underlying DARC layer 230 is also resistant to theoxygen plasma used in the RIE. Consequently, trimming of the singlelayer mask 240′ in step 108 does not significantly affect the DARC layer230.

A portion of the DARC layer 230 that does not reside under the singlelayer mask 240′ is removed, via step 110. Thus, the pattern of thesingle layer mask 240′ is transferred to the DARC layer 230. In apreferred embodiment, step 110 is performed using a fluorine plasma(e.g. CF₄) RIE. Also in a preferred embodiment, the stop layer 220 isresistant to the etch used to remove the DARC layer 230, such as thefluorine plasma RIE. As a result, step 110 may overetch the DARC layer230 without adversely affecting the underlying magnetic element layers210. Such an overetch ensures complete removal of the exposed portionsof the DARC layer 230.

FIG. 7 depicts the transducer 200 after step 110 has been performed. Ascan be seen in FIG. 7, the pattern of the single layer mask 240″ hasbeen transferred to the DARC layer 230′. Because an overetch may beperformed, the exposed portion of the DARC layer has been completelyremoved. Thus, only the portion 230′ of the DARC layer under the singlelayer mask 240″ remains. In addition, some portion of the single layermask 240″ may remain after the etch of the DARC layer.

The exposed portion of the stop layer is removed, via step 112. Stateddifferently, the pattern of the single layer mask 240′ is transferred tothe stop layer 220. If the stop layer 220 is a DLC layer, then step 112is preferably performed using an oxygen plasma RIE. However, for othermaterials, a different etch process might be used. For example, a carbonmonoxide or fluorine etch might be used if the stop layer 220 includesmaterials such as Ta, W, alumina or silicon dioxide.

FIG. 8 depicts the transducer 200 after step 112 has been performed.Because of the etch performed in step 112, only a portion of the stoplayer 220′ remains. In addition, the single layer mask 240′ may beremoved during step 112, for example using an oxygen plasma RIE orsolvent. However, a portion of the DARC layer 230″ remains, acting as amask for the underlying stop layer 220′. This is because the DARC layer230″ is preferably resistant to the etch performed in step 112.

The magnetic element is defined, via step 114. The pattern is thustransferred to the underlying magnetic element layers 210. In apreferred embodiment, step 114 is performed by ion milling the magneticelement layers, generally using Ar ions. The stop layer 220′ ispreferably insensitive to the process that defines the magnetic elementand, therefore, functions as a mask during step 114.

FIG. 9 depicts the transducer 200 after the magnetic element 210′ hasbeen defined in step 114. In the embodiment shown, the DARC layer isremoved during step 114 and is thus not depicted. The magnetic element210′ having the desired profile and desired critical dimension, d′, maythereby be formed. For example, in one embodiment, the magnetic element210′ may have a critical dimension of less than or equal to 0.08 μm, astypically measured at the free layer 218′.

Processing then continues. If a read head is being formed, then aninsulator is deposited on the magnetic element 210′, via step 116. Theinsulator is preferably alumina, but may include other materials, suchas SiO₂. A hard bias layer is provided, via step 118. Step 118 includeproviding a hard magnet used in biasing the magnetic element 210′. Inaddition, a filler is provided, via step 120. The filler is preferablyCr. However, in another embodiment, the filler provided in step 120could include other materials such as alumina, silicon dioxide, orsilicon nitride. FIG. 10 depicts the transducer 200 after step 120 hasbeen completed. Thus, the magnetic element 210′ and remaining stop layer220″ have been covered in an insulator 250, a hard bias layer 252, and afiller 254 that is preferably Cr. The filler 254 is used to protect theunderlying hard bias layer 252 from subsequent processing.

The device is planarized, via step 122. In a preferred embodiment, theplanarization is performed using a CMP step. Also in a preferredembodiment, the CMP is continued until the stop layer 220″ is exposed.

FIG. 11 depicts the transducer 200 after a portion of step 122 has beenperformed. Consequently, part of the filler layer has been removed,leaving portions 254′. A portion of the hard bias layer has also beenremoved, leaving remaining portion 252′. The exposed surface is,therefore, planar. However, as discussed above, the planarization may becontinued to overpolish the device 200. FIG. 12 depicts the transducer200 after completion of step 122. Thus, portions of the filler 254″ andhard bias 252″ remain. In addition, the insulator 250′ is exposed.However, the stop layer 220′″ remains substantially intact.Consequently, the stop layer 220′″ may still mask the underlyingmagnetic element 210′, protecting the magnetic element 210′ from damage.

The surface of the magnetic element 210′ is exposed, via step 124. Step124 may be carried out using the same etch as step 112. If the remainingportion of the stop layer 220′″ is a DLC layer, step 124 is preferablyperformed using an oxygen plasma RIE. However, for other materials, adifferent etch might be used. For example, a carbon monoxide or fluorineetch might be used if the remaining portion of the stop layer 220′″includes materials such as Ta, W, alumina or silicon dioxide. FIG. 13depicts the transducer 200 after step 124 has been performed. The topsurface of the magnetic element 210′ is thus exposed.

Processing of the device may be completed, via step 126. For thetransducer 200, step 126 may include providing contacts on the topsurface of the exposed magnetic element 210′. Additional insulating andshield layers may also be provided. If the transducer 200 is part of amerged head, then step 126 may include providing other structures, suchas a write transducer. If the magnetic element 210′ and method 100 areused for another device, then other layers and/or additional layershaving different structures and functions may be provided in step 126.

Thus, the method 100 can provide the magnetic element 210′. Because asingle layer mask 230′ is utilized, issues due to problems with lift-offand collapse of a bilayer photoresist structure can be avoided. Further,the single layer mask 230′, and thus the magnetic element 210′, can bemade smaller than the critical dimensions of photolithography. As aresult, the magnetic element can be made smaller than is possible usingconventional photolithography. In one embodiment, the magnetic element210′ can have a critical dimension of 0.08 μm or less. As a result, themethod 100 and magnetic element 210′ may be suitable for higher densityrecording applications.

1. A method for providing a magnetic element comprising; providing amagnetic element stack including a plurality of layers; depositing astop layer on the magnetic element stack; providing a dielectricantireflective coating (DARC) layer on the stop layer; forming a singlelayer mask having a first width for defining the magnetic element on afirst portion of the DARC layer; removing a second portion of the DARClayer not covered by the single layer mask, the first portion of theDARC layer covering a first portion of the stop layer; continuingremoval of the DARC layer until the first portion has a second width notlarger than the first width; removing a second portion of the stop layernot covered by the first portion of the DARC layer to form a thirdportion of the stop layer, the third portion having a third widthgreater than or equal to the second width; and defining the magneticelement using at least the third portion of stop layer as a mask.
 2. Themethod of claim 1 wherein the stop layer depositing further includes:depositing diamond-like carbon layer on the magnetic element stack. 3.The method of claim 2 wherein the remaining portion of the stop layerremoving further includes: performing an oxygen plasma reactive ionetch.
 4. The method of claim 1 wherein the stop layer depositing furtherincludes: depositing a layer include at least one of Ta, W, Alumina, andsilicon dioxide on the magnetic element stack.
 5. The method of claim 4wherein the remaining portion of the stop layer removing furtherincludes: performing an oxygen plasma reactive ion etch, a carbonmonoxide etch, or a fluorine etch.
 6. The method of claim 1 wherein theDARC layer providing step further includes: providing a layer includingat least one of SiO₃, Si_(x)N₄ and SiO_(x)N_(y).
 7. The method of claim1 wherein the remaining portion of the DARC layer not covered by thesingle layer mask removing further includes: performing a fluorineplasma reactive ion etch.
 8. The method of claim 1 wherein the singlelayer mask forming further includes: forming the single layer mask usingdeep ultra violet photoresist.
 9. The method of claim 8 wherein thesingle layer mask forming further includes: trimming the single layermask.
 10. The method of claim 1 wherein the magnetic element definingfurther includes: performing an ion milling or reactive ion etching. 11.The method of claim 1 further comprising: depositing an insulatinglayer; fabricating a hard bias layer on the insulating layer; andcreating a Cr filler layer on the hard bias layer.
 12. The method ofclaim 11 further comprising: performing a planarization, the portion ofthe stop layer acting as a planarization stop.
 13. The method of claim12 further comprising: exposing a top portion of the magnetic element.14. The method of claim 13 wherein the exposing further includes:removing at least part of the portion of the stop layer.
 15. The methodof claim 1 further comprising: depositing an insulating layer;fabricating a hard bias layer on the insulating layer; and creating afiller layer including at least one of alumina, silicon dioxide, andsilicon nitride on the hard bias layer.
 16. A method for forming amagnetic element comprising: providing a magnetic element stackincluding a plurality of layers; depositing a diamond-like carbon layeron the magnetic element stack; providing a dielectric antireflectivecoating (DARC) layer on the diamond-like carbon layer; forming a singlelayer mask having a first width for defining the magnetic element on aportion of the DARC layer, the single layer mask including a deepultra-violet photoresist; removing a second portion of the DARC layernot covered by the single layer mask using a fluorine plasma reactiveion etch, the first portion of the DARC layer covering a first portionof the diamond-like carbon layer; continuing removal of the DARC layeruntil a second width of the first portion of the DARC layer is notlarger than the first width; removing a second portion of thediamond-like carbon layer using an oxygen reactive ion etch to form athird portion of the diamond-like carbon layer, the third portion of thediamond-like carbon layer having a third width greater than or equal tothe second width; defining the magnetic element using at least theportion of diamond-like carbon layer as a mask using an ion millingstep; depositing a plurality of layers on the magnetic element includinga Cr filler layer.